Glass in building - Determination of luminous and solar characteristics of glazing

This European Standard specifies methods of determining the luminous and solar characteristics of glazing in buildings. These characteristic can serve as a basis for lighting, heating and cooling calculations of rooms and permit comparison between different types of glazing.
This European Standard applies both to conventional glazing and to absorbing or reflecting solar-control glazing, used as vertical or horizontal glazed apertures. The appropriate formulae for single, double and triple glazing are given.
This European Standard is accordingly applicable to all transparent materials except those which show significant transmission in the wavelength region 5 µm to 50 µm of ambient temperature radiation, such as certain plastic materials.
Materials with light-scattering properties for incident radiation are dealt with as conventional transparent materials subject to certain conditions (see 5.2).
Angular light and solar properties of glass in building are excluded from this Standard. However, research work in this area is summarised in E.1, E.2 and E.3.
While this European Standard presents the formulae for the exact calculations of the spectral characteristics of glazing, it does not consider the uncertainty of the measurements necessary to determine the spectral parameters that are used in the calculations. It should be noted that, for simple glazing systems where few measurements are required, the uncertainty of the results will be satisfactory if correct measurements procedures have been followed. When the glazing systems become complex and a large number of measurements are required to determine the spectral parameters, the uncertainty is cumulative with the number of measurements and should be considered in the final results.
The term interface used in this European Standard, is considered to be a surface characterized by its transmission and reflections of light intensities.

Glas im Bauwesen - Bestimmung der lichttechnischen und strahlungsphysikalischen Kenngrößen von Verglasungen

Diese Europäische Norm legt Verfahren zur Bestimmung der lichttechnischen und strahlungsphysikalischen Kenngrößen von Verglasungen von Gebäuden fest. Diese Kenngrößen können als Grundlage für licht-, heizungs- und klimatechnische Berechnungen dienen. Sie ermöglichen den Vergleich zwischen unter-schiedlichen Verglasungen. Diese Europäische Norm ist sowohl anwendbar auf übliche Verglasungen als auch auf absorbierende oder reflektierende Sonnenschutzgläser, eingesetzt in senkrechten oder waagerechten Lichtöffnungen. Die geeigneten Gleichungen für Einfach-, Doppel- und Dreifachverglasungen sind angegeben. Diese Europäische Norm ist für sämtliche lichtdurchlässige Materialien entsprechend anwendbar, ausge-nommen solche, die eine nennenswerte Transmission im Wellenlängenbereich von 5 µm bis 50 µm von Strahlung bei Raumtemperatur aufweisen, wie z. B. gewisse Kunststoffe. Materialien mit lichtstreuenden Eigenschaften für die auftreffende Strahlung werden grundsätzlich wie normale lichtdurchlässige Stoffe unter Beachtung bestimmter Bedingungen (siehe 5.2) behandelt. Die Eigenschaften von schrägem Licht und die Strahlungseigenschaften von Glas in Gebäuden werden in dieser Norm nicht erfasst. Forschungsarbeiten, die in diese Richtung gehen, werden jedoch zusammen-fassend in [1], [2] und [3] dargestellt.

Verre dans la construction - Détermination des caractéristiques lumineuses et solaires des vitrages

La présente Norme européenne spécifie les méthodes de détermination des caractéristiques lumineuses et solaires des vitrages de bâtiment. Ces caractéristiques peuvent servir de base aux calculs relatifs à l'éclairement et au conditionnement thermique des locaux et permettre d'établir des comparaisons entre différents types de vitrage. La présente Norme européenne s'applique aussi bien aux vitrages conventionnels qu'à ceux présentant des propriétés d'absorption et de réflexion de l'énergie solaire, et utilisés comme vitrages verticaux ou horizontaux. Des formules appropriées sont établies pour des vitrages simples, doubles ou triples. La présente Norme européenne s'applique à tous les matériaux transparents, à l'exception de ceux qui présentent une transmission non négligeable dans le domaine spectral de 5 µm à 50 µm du rayonnement émis par les corps à température ambiante, telles certaines feuilles de matériaux plastiques. Les matériaux caractérisés par des propriétés de diffusion du rayonnement incident sont traités comme des matériaux transparents conventionnels sous certaines réserves (voir 5.2). Les propriétés angulaires solaires et lumineuses du verre utilisé dans la construction sont exclues de la présente norme. Toutefois, les travaux de recherche dans ce domaine sont résumés en Bibliographie [1], [2] et [3].

Steklo v gradbeništvu - Določevanje svetlobnih in sončnih karakteristik stekla

Ta evropski standard določa metode za določevanje svetlobnih in sončnih karakteristik stekla v zgradbah. Te karakteristike se lahko uporabljajo kot osnova za izračune osvetljave, gretja in hlajenja prostorov in omogočajo primerjavo med različnimi vrstami stekla.
Ta evropski standard velja za konvencionalno steklo in za absorpcijsko ali odsevno steklo za nadzor sonca, ki se uporablja kot navpična ali vodoravna steklena odprtina. Podane so ustrezne formule za enojno, dvojno in trojno steklo.
Ta evropski standard ustrezno velja za vse prosojne materiale, razen za tiste, ki kažejo bistveno prepustnost v območju valovnih dolžin med 5 µm in 50 µm sevanja okoljske temperature, kot so nekateri plastični materiali.
Materiali z lastnostmi sipanja svetlobe za naključno sevanje se obravnavajo kot konvencionalni prosojni materiali ob upoštevanju nekaterih zahtev (glej 5.2).
Kotna svetloba in sončne lastnosti stekla v gradbeništvu so izvzete iz tega standarda. Raziskovalno delo s tega področja pa je povzeto v E.1, E.2 in E.3.
Medtem ko ta evropski standard predstavlja formule za natančne izračune spektralnih lastnosti stekla, ne obravnava negotovosti potrebnih meritev za določanje spektralnih parametrov, ki se uporabljajo pri izračunih. Treba je upoštevati, da je pri preprostih steklenih sistemih, pri katerih je potrebnih le malo meritev, negotovost rezultatov zadovoljiva, če se upoštevajo pravilni postopki merjenja. Če pa so stekleni sistemi kompleksni in je za določanje spektralnih parametrov potrebno več meritev, je negotovost kumulativna glede na število meritev in se mora upoštevati pri končnih rezultatih.
Izraz vmesnik, ki se uporablja v tem evropskem standardu, je površina, ki jo označujeta prosojnost in odsevi svetlobnih intenzitet.

General Information

Status
Published
Publication Date
08-Feb-2011
Current Stage
9092 - Decision on results of review/2YR ENQ - revise - Review Enquiry
Completion Date
02-May-2019

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Glas im Bauwesen - Bestimmung der lichtechnischen und trahlungsphysikalischen Kenngrößssen von VerglasungenVerre dans la construction - Détermination des caractéristiques lumineuses et solaires des vitragesGlass in building - Determination of luminous and solar characteristics of glazing81.040.20Steklo v gradbeništvuGlass in buildingICS:Ta slovenski standard je istoveten z:EN 410:2011SIST EN 410:2011en,fr,de01-junij-2011SIST EN 410:2011SLOVENSKI

STANDARDSIST EN 410:19991DGRPHãþD
SIST EN 410:2011
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 410
February 2011 ICS 81.040.20 Supersedes EN 410:1998English Version

Glass in building - Determination of luminous and solar characteristics of glazing

Verre dans la construction - Détermination des caractéristiques lumineuses et solaires des vitrages

Glas im Bauwesen - Bestimmung der lichttechnischen und strahlungsphysikalischen Kenngrößen von Verglasungen This European Standard was approved by CEN on 2 January 2011.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,

B-1000 Brussels © 2011 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 410:2011: ESIST EN 410:2011

EN 410:2011 (E) 2 Contents Page Foreword ..............................................................................................................................................................3Introduction .........................................................................................................................................................41Scope ......................................................................................................................................................52Normative references ............................................................................................................................53Terms and definitions ...........................................................................................................................54Symbols ..................................................................................................................................................65Determination of characteristics ..........................................................................................................85.1General ....................................................................................................................................................85.2Light transmittance................................................................................................................................85.3Light reflectance ................................................................................................................................. 115.4Total solar energy transmittance (solar factor) ............................................................................... 125.4.1Calculation ........................................................................................................................................... 125.4.2Division of incident solar radiant flux............................................................................................... 125.4.3Solar direct transmittance ................................................................................................................. 145.4.4Solar direct reflectance ...................................................................................................................... 145.4.5Solar direct absorptance .................................................................................................................... 145.4.6Secondary heat transfer factor towards the inside ......................................................................... 145.5UV-transmittance ................................................................................................................................ 195.6Colour rendering ................................................................................................................................. 195.7Shading coefficient ............................................................................................................................. 226Expression of results ......................................................................................................................... 237Test report ........................................................................................................................................... 23Annex A

(normative)

Procedures for calculation of the spectral characteristics of glass plates with a different thickness and/or colour .......................................................................................... 33Annex B (normative)

Procedure for calculation of the spectral characteristics of laminated glass ...... 38Annex C (informative)

Procedure for calculation of the spectral characteristics of screen printed glass ..................................................................................................................................................... 59Annex D (informative)

Example of calculation of colour rendering index ................................................. 60Bibliography ..................................................................................................................................................... 64 SIST EN 410:2011

EN 410:2011 (E) 3 Foreword This document (EN 410:2011) has been prepared by Technical Committee CEN/TC 129 “Glass in building”, the secretariat of which is held by NBN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by August 2011, and conflicting national standards shall be withdrawn at the latest by August 2011. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 410:1998. The main changes compared to the previous edition are: a) A procedure is provided for the calculation of the spectral properties of laminated glass.

b) A formula is introduced for determining the total shading coefficient.
c) Table 3 has been updated to make it more practical.

d) Table 6 has been updated in line with the 2004 edition of the publication CIE No 15.

e) The external and internal heat transfer coefficients have been amended slightly to reflect changes to EN 673.

f) Guidance is also given on how to determine the spectral characteristics of screen printed glass.

g) New drawings have been introduced for improved clarity and to conform with CEN rules.

This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s). According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. SIST EN 410:2011

EN 410:2011 (E) 4 Introduction While this European Standard presents the formulae for the exact calculations of the spectral characteristics of glazing, it does not consider the uncertainty of the measurements necessary to determine the spectral parameters that are used in the calculations. It should be noted that, for simple glazing systems where few measurements are required, the uncertainty of the results will be satisfactory if correct measurements procedures have been followed. When the glazing systems become complex and a large number of measurements are required to determine the spectral parameters, the uncertainty is cumulative with the number of measurements and should be considered in the final results.

The term interface used in this European Standard, is considered to be a surface characterized by its transmission and reflections of light intensities. That is, the interaction with light is incoherent, all phase information being lost. In the case of thin films (not described in this European Standard), interfaces are characterized by transmission and reflections of light amplitudes, i.e. the interaction with light is coherent and phase information is available. Finally, for clarity, a coated interface can be described as having one or more thin films, but the entire stack of thin films is characterized by its resulting transmission and reflection of light intensities. In Annex B, the procedure for the calculation of spectral characteristics of laminated glass makes specific reference to coated glass. The same procedure can be adopted for filmed glass (e.g. adhesive backed polymeric film applied to glass). SIST EN 410:2011

EN 410:2011 (E) 5

1 Scope This European Standard specifies methods of determining the luminous and solar characteristics of glazing in buildings. These characteristic can serve as a basis for lighting, heating and cooling calculations of rooms and permit comparison between different types of glazing. This European Standard applies both to conventional glazing and to absorbing or reflecting solar-control glazing, used as vertical or horizontal glazed apertures. The appropriate formulae for single, double and triple glazing are given. This European Standard is accordingly applicable to all transparent materials except those which show significant transmission in the wavelength region 5 µm to 50 µm of ambient temperature radiation, such as certain plastic materials. Materials with light-scattering properties for incident radiation are dealt with as conventional transparent materials subject to certain conditions (see 5.2). Angular light and solar properties of glass in building are excluded from this standard. However, research work in this area is summarised in Bibliography [1], [2] and [3].

2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 673, Glass in building — Determination of thermal transmittance (U value) — Calculation method EN 674, Glass in building — Determination of thermal transmittance (U value) — Guarded hot plate method EN 675, Glass in building — Determination of thermal transmittance (U value) — Heat flow meter method EN 12898, Glass in building — Determination of the emissivity

3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 light transmittance fraction of the incident light that is transmitted by the glass 3.2 light reflectance fraction of the incident light that is reflected by the glass 3.3 total solar energy transmittance (solar factor) fraction of the incident solar radiation that is totally transmitted by the glass SIST EN 410:2011

EN 410:2011 (E) 6 3.4 solar direct transmittance fraction of incident solar radiation that is directly transmitted by the glass 3.5 normal emissivity ratio, in a direction normal to the surface, of the emissive power of the surface of the glass to the emissive power of a black body

NOTE Normal emissivity is determined in accordance with EN 12898. 3.6 solar direct reflectance fraction of the incident solar radiation that is reflected by the glass 3.7 ultraviolet transmittance fraction of the incident UV component of the solar radiation that is transmitted by the glass 3.8 colour rendering index (in transmission) change in colour of an object as a result of the light being transmitted by the glass 3.9 shading coefficient ratio of the solar factor of the glass to the solar factor of a reference glass (clear float) 4 Symbols Sym. Deutsch/German/Allemand Englisch/English/Anglais Französisch/French/Français D65 Normlichtart D65 standard illuminant D65 illuminant normalisé D65 UV Ultravioletter Strahlungsbereich ultraviolet radiation rayonnement ultraviolet UV

Ultravioletter Transmissionsgrad ultraviolet transmittance facteur de transmission de l'ultraviolet

Spektraler Transmissionsgrad spectral transmittance facteur de transmission spectrale

Spektraler Reflexionsgrad spectral reflectance facteur de réflexion spectrale
Lichtransmissionsgrad light transmittance facteur de transmission lumineuse
Lichtreflexionsgrad light reflectance facteur de réflexion lumineuse

direkter Strahlungstrans- missionsgrad solar direct transmittance facteur de transmission directe de l'énergie solaire

direkter Strahlungs- reflexionsgrad solar direct reflectance facteur de réflexion directe de l'énergie solaire SIST EN 410:2011

EN 410:2011 (E) 7

Gesamtenergiedurchlaß- grad total solar energy transmittance (solar factor) facteur de transmission totale de l'énergie solaire ou facteur solaire Ra allgemeiner Farbwieder- gabeindex general colour rendering index indice général de rendu des couleurs D relative spektrale Vertei- lung der Normlichtart D65 relative spectral distribution of illuminant D65 répartition spectrale relative de l'illuminant normalisé D65 V() spektraler Hellempfindlich- keitsgrad spectral luminous efficiency efficacité lumineuse relative spectrale

direkter Strahlungsabsorp tionsgrad solar direct absorptance facteur d'absorption directe de l'énergie solaire

Strahlungsleistung (Strahlungsfluß) incident solar radiant flux flux énergétique solaire incident

sekundärer Wärmeabgabe- grad nach innen secondary internal heat transfer factor facteur de réémission thermique vers l'intérieur

sekundärer Wärme- abgabegrad nach außen secondary external heat transfer factor facteur de réémission thermique vers l'extérieur

relative spektrale Vertei- lung der Sonnenstrahlung relative spectral distribution of solar radiation répartition spectrale relative du rayonnement solaire

Wärmeübergangs- koeffizient nach außen external heat transfer coefficient coefficient d'échange thermique extérieur

Wärmeübergangs- koeffizient nach innen internal heat transfer coefficient coefficient d'échange thermique intérieur

korrigierter Emissionsgrad corrected emissivity émissivité corrigée
n normaler Emissionsgrad normal emissivity émissivité normale
Wärmedurchlaßkoeffizient thermal conductance conductance thermique
Wellenlänge wavelength longueur d'onde
Wellenlängenintervall wavelength interval intervalle de longueur d'onde

relative spektrale Vertei- Lung der UV-Strahlung der Sonne relative spectral distribution of UV in solar radiation répartition spectrale relative du rayonnement ultraviolet solaire SC Durchlassfaktor shading coefficient coefficient d’ombrage

SIST EN 410:2011

EN 410:2011 (E) 8 5 Determination of characteristics 5.1 General The characteristics are determined for quasi-parallel, near normal radiation incidence (see Bibliography, [4]) using the radiation distribution of illuminant D65 (see Table 1), solar radiation in accordance with Table 2 and ultraviolet (UV) radiation in accordance with Table 3. The characteristics are as follows:  the spectral transmittance

and the spectral reflectance
in the wavelength range from 300 nm to 2500 nm;
 the light transmittance
and the light reflectance
for illuminant D65;  the solar direct transmittance
and the solar direct reflectance ;
 the total solar energy transmittance (solar factor) g ;

 the UV-transmittance ;  the general colour rendering index Ra;  the total shading coefficient, SC. To characterize glazing, the principal parameters are

and g; the other parameters are optional to provide additional information. If the value of a given characteristic is required for different glass thicknesses (in the case of uncoated glass) or for the same coating applied to different substrates, it can be obtained by calculation (in accordance with Annex A). A procedure for the calculation of the spectral characteristics of laminated glass is given in Annex B. Guidelines on determining the spectral characteristics of screen printed glass are given in Annex C. 5.2 Light transmittance The light transmittance

of the glazing is calculated using the following formula:
(1) where
is the relative spectral distribution of illuminant D65 (see Bibliography [5]);
is the spectral transmittance of the glazing;

is the spectral luminous efficiency for photopic vision defining the standard observer for photometry (see Bibliography [5]);

is the wavelength interval. SIST EN 410:2011

EN 410:2011 (E) 9 Table 1 indicates the values for for wavelength intervals of 10 nm. The table has been drawn up in such a way that . In the case of multiple glazing, the spectral transmittances

are calculated from the spectral transmittances and reflectances of the individual components as follows :

For double glazing:
(2) where
is the spectral transmittance of the first (outer) pane;
is the spectral transmittance of the second pane;

is the spectral reflectance of the first (outer) pane, measured in the direction opposite to the incident radiation;

is the spectral reflectance of the second pane, measured in the direction of the incident radiation. The above is illustrated in Figure 1. SIST EN 410:2011

EN 410:2011 (E) 10

Key 1 pane 1 2 cavity 3 pane 2 Figure 1 — Transmittance and reflectance in a double glazing insulating glass unit For triple glazing:

(3) where , ,
and
are as explained in Equation (2);
is the spectral transmittance of the third pane;

is the spectral reflectance of the second pane, measured in the direction opposite to the incident radiation;

is the spectral reflectance of the third pane, measured in the direction of the incident radiation. The above is illustrated in Figure 2.

SIST EN 410:2011
EN 410:2011 (E) 11

Key 1 pane 1 2 cavity 1 3 pane 2 4 cavity 2 5 pane 3 Figure 2 — Transmittance and reflectance in a triple glazing insulating glass unit For glazing with more than three components, formulae similar to Equations (2) and (3) are found to calculate

of such glazing from the spectral coefficients of the individual components. As an example, glazing composed of five components may be treated as follows: a) first consider the first three components as triple glazing and calculate the spectral characteristics of this combination; b) next, run the same procedure for the next two components as double glazing; c) then calculate

for the five component glazing, considering it as double glazing consisting of the preceding triple and double glazing. NOTE 1 The use of an integrating sphere is necessary when light scattering materials are tested. In this case the size of the sphere and its aperture shall be large enough to collect all possible scattered light and to obtain fair average values when surface patterns are irregularly distributed. NOTE 2 Measurement of light scattering glass products is the subject of a round robin test programme under the responsibility of International Commission on Glass Technical Committee 10. The results of this programme are expected to include suggestions for improvements in measurement and prediction techniques. 5.3 Light reflectance The light reflectance of the glazing

is calculated using the following formula:
(4) where
and
are as explained in 5.2;
is the spectral reflectance of the glazing. SIST EN 410:2011
EN 410:2011 (E) 12 In the case of multiple glazing, the spectral reflectance

is calculated from the spectral transmittances and the spectral reflectances of the individual components as follows. For double glazing, the external light reflectance of the glazing is calculated as follows:

(5) where ,
and
are as explained in 5.2;

is the spectral reflectance of the first (outer) pane, measured in the direction of incident radiation. A corresponding equation can also be derived for calculating the internal light reflectance. For triple glazing, the external light reflectance of the glazing is calculated as follows:

(6) where

is the spectral reflectance of the third pane, measured in the direction of the incident radiation; , , , ,

and

are as defined in 5.2 and 5.3. A corresponding equation the internal light reflectance of triple glazing can also be derived. For glazing with more than three elements the same method as described in 5.2 is used. 5.4 Total solar energy transmittance (solar factor) 5.4.1 Calculation The total solar energy transmittance

is calculated as the sum of the solar direct transmittance
and the secondary heat transfer factor

of the glazing towards the inside (see 5.4.3 and 5.4.6), the latter resulting from heat transfer by convection and longwave IR-radiation of that part of the incident solar radiation which has been absorbed by the glazing:

(7) 5.4.2 Division of incident solar radiant flux The incident solar radiant flux

is divided into the following three parts (see Figure 3): a) the transmitted part, ; b) the reflected part, ; c) the absorbed part, ; SIST EN 410:2011

EN 410:2011 (E) 13 where
is the solar direct transmittance (see 5.4.3);
is the solar direct reflectance (see 5.4.4);
is the solar direct absorptance (see 5.4.5).

Key 1 outer pane 2 second inner pane 3 unit incident radiant flux Figure 3 — Example of division of the incident radiant flux The relation between the three characteristics is:

(8) The absorbed part
is subsequently split into two parts
and
which are energy transferred to the inside and outside respectively:
(9) where
is the secondary heat transfer factor of the glazing towards the inside;

is the secondary heat transfer factor of the glazing towards the outside. SIST EN 410:2011

EN 410:2011 (E) 14 5.4.3 Solar direct transmittance The solar direct transmittance

of the glazing is calculated using the following formula:
(10) where
is the relative spectral distribution of the solar radiation (see Table 2);
is the spectral transmittance of the glazing;

is the wavelength interval. In the case of multiple glazing, the spectral transmittance

is calculated in accordance with 5.2. The relative spectral distribution, , used to calculate the solar direct transmittance is derived from CIE 85 [6]. The corresponding values

are given in Table 2. The table was drawn up in such a way that . NOTE Contrary to real situations, it is always assumed, for simplification, that the spectral distribution of the solar radiation (see Table 2) is not dependent upon atmospheric conditions (e.g. dust, mist, moisture content) and that the solar radiation strikes the glazing as a collimated beam and at normal incidence. The resulting errors are very small. 5.4.4 Solar direct reflectance The solar direct reflectance

of the glazing is calculated using the following formula:
(11) where
is the relative spectral distribution of the solar radiation (see Table 2);
is the spectral reflectance of the glazing;

is the wavelength interval. In the case of multiple glazing, the spectral reflectance

is calculated in accordance with 5.3. 5.4.5 Solar direct absorptance The solar direct absorptance

is calculated from Equation (8) in 5.4.2. 5.4.6 Secondary heat transfer factor towards the inside 5.4.6.1 Boundary conditions For the calculation of the secondary heat transfer factor towards the inside, , the heat transfer coefficients of the glazing towards the outside, , and towards the inside,

are needed. These values mainly depend on SIST EN 410:2011

EN 410:2011 (E) 15 the position of the glazing, wind velocity, inside and outside temperatures and furthermore on the temperature of the two external glazing surfaces. As the purpose of this standard is to provide basic information on the performance of glazing, conventional conditions have been stated for simplicity: a) position of the glazing: vertical; b) outside surface: wind velocity: approximately 4 m/s, corrected emissivity = 0,837; c) inside surface: natural convection, emissivity optional; d) air spaces are unventilated. Under these conventional, average conditions, standard values for

and
are obtained:
where

is the corrected emissivity of the inside surface. For uncoated soda lime silicate glass and borosilicate glass

and .

The corrected emissivity shall be defined and measured in accordance with EN 12898. NOTE Values lower than 0,837 for

(due to surface coatings with higher reflectance in the far infra-red) are only to be taken into account if condensation on the coated surface can be excluded. 5.4.6.2 Single glazing The secondary internal heat transfer factor, , of single glazing is calculated using the following formula:

(12) where
is the solar direct absorptance in accordance with 5.4.5;
and

are the heat transfer coefficients towards the outside and inside respectively in accordance with 5.4.6.1. 5.4.6.3 Double glazing The secondary internal heat transfer factor, qi, of double glazing is calculated using the following formula:

(13) SIST EN 410:2011
EN 410:2011 (E) 16 where
and

are the heat transfer coefficients towards the outside and inside respectively in accordance with 5.4.6.1;

is the solar direct absorptance of the outer pane within the double glazing;
is the solar direct absorptance of the second pane within the double glazing;

is the thermal conductance between the outer surface and the innermost surface of the double glazing (see Figure 4).

and
are calculated as follows:
(14)
(15) where

is the spectral direct absorptance of the outer pane, measured in the direction of the incident radiation, given by the formula:

(16)

is the spectral direct absorptance of the outer pane, measured in the opposite direction to the incident radiation, given by the formula:

(17)

is the spectral direct absorptance of the second pane, measured in the direction of the incident radiation, given by the formula:

(18)
and
are as defined in 5.4.3; ,
and
are as defined in 5.2. The thermal conductance

is determined by the calculation method in accordance with EN 673 whenever possible or by measuring methods in accordance with EN 674 or EN 675.

SIST EN 410:2011
EN 410:2011 (E) 17

Key 1 pane 1 2 pane 2 3 outside 4 inside Figure 4 — Illustration of the meaning of thermal conductance

5.4.6.4 Triple glazing The secondary internal heat transfer factor of triple glazing, , is calculated using the following formula:

(19) where
is the solar direct absorptance of the outer pane within the triple glazing;
is the solar direct absorptance of the second pane within the triple glazing;
is the solar direct absorptance of the third pane within the triple glazing;
and

are the heat transfer coefficients towards the outside and inside respectively in accordance with 5.4.6.1;

is the thermal conductance between the outer surface of the first pane and the centre of the second pane (see Figure 5);

is the thermal conductance between the centre of the second pane and the innermost surface of the third pane (see Figure 5).

SIST EN 410:2011
EN 410:2011 (E) 18

Key 1 pane 1 2 pane 2 3 pane 3 4 outside 5 inside Figure 5 — Illustration of the meaning of the thermal conductances

and
and
are calculated as follows:
(20)
(21)
(22) where ,
and
are as defined in 5.4.6.3;

is the spectral direct absorptance of the second pane, measured in the opposite direction to the incident radiation, given by the formula:

(23) SIST EN 410:2011
EN 410:2011 (E) 19

is the spectral direct absorptance of the third pane, measured in the direction of the incident radiation, given by the formula:

(24)
and
are as defined in 5.4.3. The thermal conductances
and

are determined in accordance with 5.4.6.3. 5.5 UV-transmittance In the UV range, the global radiation of the sun contains components in the UV-B range 280 nm to 315 nm and the UV-A range 315 nm to 380 nm. A standard relative spectral distribution for the UV part of the global solar radiation, , is given (see Bibliography, [7]). Table 3 gives the values of

for wavelength intervals of 5 nm in the UV range. The table has been drawn up with relative values in such a way that

for the total UV range. The UV-transmittance
is calculated as follows:
(25) where
is the spectral direct transmittance of the glazing (see 5.2);
is the relative distribution of the UV part of global solar radiation;

is the wavelength interval. NOTE If statements are made about the UV transmission of glazing, in most cases it is sufficient to give , the transmittance for the total UV radiation contained in global solar radiation. Only in special cases would there be any interest in the transmittances for the sub-ranges UV-A and UV-B. 5.6 Colour rendering The colour rendering properties of glazing in transmission

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Glas im Bauwesen - Bestimmung der lichtechnischen und trahlungsphysikalischen Kenngrößssen von VerglasungenVerre dans la construction - Détermination des caractéristiques lumineuses et solaires des vitragesGlass in building - Determination of luminous and solar characteristics of glazing81.040.20Steklo v gradbeništvuGlass in buildingICS:Ta slovenski standard je istoveten z:FprEN 410kSIST FprEN 410:2010en,fr,de01-september-2010kSIST FprEN 410:2010SLOVENSKI

STANDARD
kSIST FprEN 410:2010
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
FINAL DRAFT
FprEN 410
July 2010 ICS 81.040.20 Will supersede EN 410:1998English Version

Glass in building - Determination of luminous and solar characteristics of glazing

Verre dans la construction - Détermination des caractéristiques lumineuses et solaires des vitrages

Glas im Bauwesen - Bestimmung der lichtechnischen und trahlungsphysikalischen Kenngrößssen von VerglasungenThis draft European Standard is submitted to CEN members for unique acceptance procedure. It has been drawn up by the Technical Committee CEN/TC 129.

If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre:
Avenue Marnix 17,

B-1000 Brussels © 2010 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. FprEN 410:2010: EkSIST FprEN 410:2010

FprEN 410:2010 (E) 2 Contents Page Foreword ..............................................................................................................................................................31Scope ......................................................................................................................................................42Normative references ............................................................................................................................43Terms and definitions ...........................................................................................................................54Symbols ..................................................................................................................................................55Determination of characteristics ..........................................................................................................75.1General ....................................................................................................................................................75.2Light transmittance................................................................................................................................75.3Light reflectance ................................................................................................................................. 105.4Total solar energy transmittance (solar factor) ............................................................................... 105.4.1Calculation ........................................................................................................................................... 105.4.2Division of incident solar radiant flux............................................................................................... 115.4.3Solar direct transmittance ................................................................................................................. 125.4.4Solar direct reflectance ...................................................................................................................... 135.4.5Solar direct absorptance .................................................................................................................... 135.4.6Secondary heat transfer factor towards the inside ......................................................................... 135.5UV-transmittance ................................................................................................................................ 185.6Colour rendering ................................................................................................................................. 185.7Shading coefficient ............................................................................................................................. 216Expression of results ......................................................................................................................... 217Test report ........................................................................................................................................... 21Annex A

(normative)

Procedures for calculation of the spectral characteristics of glass plates with a different thickness and/or colour .......................................................................................... 31Annex B (normative)

Procedure for calculation of the spectral characteristics of laminated glass ...... 36Annex C (informative)

Procedure for calculation of the spectral characteristics of screen printed glass ..................................................................................................................................................... 55Annex D (informative)

Example of calculation of colour rendering index ................................................. 56Bibliography ..................................................................................................................................................... 60 kSIST FprEN 410:2010

FprEN 410:2010 (E) 3 Foreword This document (FprEN 410:2010) has been prepared by Technical Committee CEN/TC 129 “Glass in building”, the secretariat of which is held by NBN. This document is currently submitted to the Unique Acceptance Procedure. This document will supersede EN 410:1998. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s).

kSIST FprEN 410:2010

FprEN 410:2010 (E) 4 1 Scope This European Standard specifies methods of determining the luminous and solar characteristics of glazing in buildings. These characteristic can serve as a basis for lighting, heating and cooling calculations of rooms and permit comparison between different types of glazing. This European Standard applies both to conventional glazing and to absorbing or reflecting solar-control glazing, used as vertical or horizontal glazed apertures. The appropriate formulae for single, double and triple glazing are given. This European Standard is accordingly applicable to all transparent materials except those which show significant transmission in the wavelength region 5 µm to 50 µm of ambient temperature radiation, such as certain plastic materials. Materials with light-scattering properties for incident radiation are dealt with as conventional transparent materials subject to certain conditions (see 5.2). Angular light and solar properties of glass in building are excluded from this Standard. However, research work in this area is summarised in E.1, E.2 and E.3. While this European Standard presents the formulae for the exact calculations of the spectral characteristics of glazing, it does not consider the uncertainty of the measurements necessary to determine the spectral parameters that are used in the calculations. It should be noted that, for simple glazing systems where few measurements are required, the uncertainty of the results will be satisfactory if correct measurements procedures have been followed. When the glazing systems become complex and a large number of measurements are required to determine the spectral parameters, the uncertainty is cumulative with the number of measurements and should be considered in the final results.

The term interface used in this European Standard, is considered to be a surface characterized by its transmission and reflections of light intensities. That is, the interaction with light is incoherent, all phase information being lost. In the case of thin films (not described in this European Standard), interfaces are characterized by transmission and reflections of light amplitudes, i.e. the interaction with light is coherent and phase information is available. Finally, for clarity, a coated interface can be described as having one or more thin films, but the entire stack of thin films is characterized by its resulting transmission and reflection of light intensities. In Annex B, the procedure for the calculation of spectral characteristics of laminated glass makes specific reference to coated glass. The same procedure can be adopted for filmed glass (e.g. adhesive backed polymeric film applied to glass). 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 673, Glass in building — Determination of thermal transmittance (U value) — Calculation method EN 674, Glass in building — Determination of thermal transmittance (U value) — Guarded hot plate method EN 675, Glass in building — Determination of thermal transmittance (U value) — Heat flow meter method EN 12898, Glass in building — Determination of the emissivity

kSIST FprEN 410:2010

FprEN 410:2010 (E) 5 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 light transmittance fraction of the incident light that is transmitted by the glass 3.2 light reflectance fraction of the incident light that is reflected by the glass 3.3 total solar energy transmittance (solar factor) fraction of the incident solar radiation that is totally transmitted by the glass 3.4 solar direct transmittance fraction of incident solar radiation that is directly transmitted by the glass 3.5 normal emissivity ratio, in a direction normal to the surface, of the emissive power of the surface of the glass to the emissive power of a black body (see EN 12898) 3.6 solar direct reflectance fraction of the incident solar radiation that is reflected by the glass 3.7 ultraviolet transmittance fraction of the incident UV component of the solar radiation that is transmitted by the glass 3.8 colour rendering index (in transmission) change in colour of an object as a result of the light being transmitted by the glass 3.9 shading coefficient ratio of the solar factor of the glass to the solar factor of a reference glass (clear float) 4 Symbols Sym. Deutsch/German/Allemand Englisch/English/Anglais Französisch/French/FrançaisD65 Normlichtart D65 standard illuminant D65 illuminant normalisé D65 UV Ultravioletter Strahlungsbereich ultraviolet radiation rayonnement ultraviolet UV

Ultravioletter Transmissionsgrad ultraviolet transmittance facteur de transmission de l'ultraviolet

Spektraler Transmissionsgrad spectral transmittance facteur de transmission spectrale kSIST FprEN 410:2010

FprEN 410:2010 (E) 6
Spektraler Reflexionsgrad spectral reflectance facteur de réflexion spectrale
Lichtransmissionsgrad light transmittance facteur de transmission lumineuse
Lichtreflexionsgrad light reflectance facteur de réflexion lumineuse

direkter Strahlungstrans- missionsgrad solar direct transmittance facteur de transmission directe de l' énergie solaire

direkter Strahlungs- reflexionsgrad solar direct reflectance facteur de réflexion directe de l'énergie solaire

Gesamtenergiedurchlaß- grad total solar energy transmittance (solar factor) facteur de transmission totale de l'énergie solaire ou facteur solaire Ra allgemeiner Farbwieder- gabeindex general colour rendering index indice général de rendu des couleurs D relative spektrale Vertei- lung der Normlichtart D65 relative spectral distribution of illuminant D65 répartition spectrale relative de l'illuminant normalisé D65 V() spektraler Hellempfindlich- keitsgrad spectral luminous efficiency efficacité lumineuse relative spectrale

direkter Strahlungsabsorp tionsgrad solar direct absorptance facteur d'absorption directe de l'énergie solaire

Strahlungsleistung (Strahlungsfluß) incident solar radiant flux flux énergétique solaire incident

sekundärer Wärmeabgabe- grad nach innen secondary internal heat transfer factor facteur de réémission thermique vers l'intérieur

sekundärer Wärme- abgabegrad nach außen secondary external heat transfer factor facteur de réémission thermique vers l'extérieur

relative spektrale Vertei- lung der Sonnenstrahlung relative spectral distribution of solar radiation répartition spectrale relative du rayonnement solaire

Wärmeübergangs- koeffizient nach außen external heat transfer coefficient coefficient d'échange thermique extérieur

Wärmeübergangs- koeffizient nach innen internal heat transfer coefficient coefficient d'échange thermique intérieur

korrigierter Emissionsgrad corrected emissivity émissivité corrigée
Wärmedurchlaßkoeffizient thermal conductance conductance thermique
Wellenlänge wavelength longueur d'onde kSIST FprEN 410:2010
FprEN 410:2010 (E) 7
Wellenlängenintervall wavelength interval intervalle de longueur d'onde

relative spektrale Vertei- Lung der UV-Strahlung der Sonne relative spectral distribution of UV in solar radiation répartition spectrale relative du rayonnement ultraviolet solaire SC Durchlassfaktor shading coefficient coefficient d’ombrage

5 Determination of characteristics 5.1 General The characteristics are determined for quasi-parallel, near normal radiation incidence (see E.4) using the radiation distribution of illuminant D65 (see Table 1), solar radiation in accordance with Table 2 and ultraviolet (UV) radiation in accordance with Table 3. The characteristics are as follows:  the spectral transmittance

and the spectral reflectance
in the wavelength range from 300 nm to 2500 nm;
 the light transmittance
and the light reflectance
for illuminant D65;  the solar direct transmittance
and the solar direct reflectance ;
 the total solar energy transmittance (solar factor) g ;

 the UV-transmittance ;  the general colour rendering index Ra;  the total shading coefficient, SC. To characterize glazing, the principal parameters are

and g; the other parameters are optional to provide additional information. If the value of a given characteristic is required for different glass thicknesses (in the case of uncoated glass) or for the same coating applied to different substrates, it can be obtained by calculation (in accordance with Annex A). A procedure for the calculation of the spectral characteristics of laminated glass is given in Annex B. Guidelines on determining the spectral characteristics of screen printed glass are given in Annex C. 5.2 Light transmittance The light transmittance

of the glazing is calculated using the following formula:
(1) kSIST FprEN 410:2010
FprEN 410:2010 (E) 8 where
is the relative spectral distribution of illuminant D65 (see D.2);
is the spectral transmittance of the glazing;

is the spectral luminous efficiency for photopic vision defining the standard observer for photometry (see D.2);

is the wavelength interval. Table 1 indicates the values for for wavelength intervals of 10 nm. The table has been drawn up in such a way that . In the case of multiple glazing, the spectral transmittances

are calculated from the spectral transmittances and reflectances of the individual components as follows :

For double glazing:
(2) where
is the spectral transmittance of the first (outer) pane;
is the spectral transmittance of the second pane;

is the spectral reflectance of the first (outer) pane, measured in the direction opposite to the incident radiation;

is the spectral reflectance of the second pane, measured in the direction of the incident radiation. The above is illustrated in Figure 1.

Figure 1 — Transmittance and reflectance in a double glazing insulating glass unit kSIST FprEN 410:2010

FprEN 410:2010 (E) 9 For triple glazing:
(3) where , ,
and
are as explained in Equation (2);
is the spectral transmittance of the third pane;

is the spectral reflectance of the second pane, measured in the direction opposite to the incident radiation;

is the spectral reflectance of the third pane, measured in the direction of the incident radiation. The above is illustrated in Figure 2.

Figure 2 — Transmittance and reflectance in a triple glazing insulating glass unit For glazing with more than three components, formulae similar to Equations (2) and (3) are found to calculate

of such glazing from the spectral coefficients of the individual components. As an example, glazing composed of five components may be treated as follows: a) first consider the first three components as triple glazing and calculate the spectral characteristics of this combination; b) next, run the same procedure for the next two components as double glazing; c) then calculate

for the five component glazing, considering it as double glazing consisting of the preceding triple and double glazing. NOTE 1 The use of an integrating sphere is necessary when light scattering materials are tested. In this case the size of the sphere and its aperture shall be large enough to collect all possible scattered light and to obtain fair average values when surface patterns are irregularly distributed. NOTE 2 Measurement of light scattering glass products is the subject of a round robin test programme under the responsibility of International Commission on Glass Technical Committee 10. The results of this programme are expected to include suggestions for improvements in measurement and prediction techniques. kSIST FprEN 410:2010

FprEN 410:2010 (E) 10 5.3 Light reflectance The light reflectance of the glazing
is calculated using the following formula:
(4) where
and
are as explained in 5.2;

is the spectral reflectance of the glazing. In the case of multiple glazing, the spectral reflectance

is calculated from the spectral transmittances and the spectral reflectances of the individual components as follows. For double glazing, the external light reflectance of the glazing is calculated as follows:

(5) where ,
and
are as explained in 5.2;

is the spectral reflectance of the first (outer) pane, measured in the direction of incident radiation. A corresponding equation can also be derived for calculating the internal light reflectance. For triple glazing, the external light reflectance of the glazing is calculated as follows:

(6) where

is the spectral reflectance of the third pane, measured in the direction of the incident radiation; , , , ,

and

are as defined in 5.2 and 5.3. A corresponding equation the internal light reflectance of triple glazing can also be derived. For glazing with more than three elements the same method as described in 5.2 is used. 5.4 Total solar energy transmittance (solar factor) 5.4.1 Calculation The total solar energy transmittance

is calculated as the sum of the solar direct transmittance
and the secondary heat transfer factor

of the glazing towards the inside (see 5.4.3 and 5.4.6), the latter resulting kSIST FprEN 410:2010

FprEN 410:2010 (E) 11 from heat transfer by convection and longwave IR-radiation of that part of the incident solar radiation which has been absorbed by the glazing:

(7) 5.4.2 Division of incident solar radiant flux The incident solar radiant flux

is divided into the following three parts (see Figure 3): a) the transmitted part, ; b) the reflected part, ; c) the absorbed part, ; where

is the solar direct transmittance (see 5.4.3);
is the solar direct reflectance (see 5.4.4);
is the solar direct absorptance (see 5.4.5).
kSIST FprEN 410:2010
FprEN 410:2010 (E) 12

Figure 3 — Example of division of the incident radiant flux The relation between the three characteristics is:

(8) The absorbed part
is subsequently split into two parts
and
which are energy transferred to the inside and outside respectively:
(9) where
is the secondary heat transfer factor of the glazing towards the inside;

is the secondary heat transfer factor of the glazing towards the outside. 5.4.3 Solar direct transmittance The solar direct transmittance

of the glazing is calculated using the following formula: kSIST FprEN 410:2010
FprEN 410:2010 (E) 13
(10) where
is the relative spectral distribution of the solar radiation (see Table 2);
is the spectral transmittance of the glazing;

is the wavelength interval. In the case of multiple glazing, the spectral transmittance

is calculated in accordance with 5.2. The relative spectral distribution, , used to calculate the solar direct transmittance is derived from D.3. The corresponding values

are given in Table 2. The table was drawn up in such a way that . NOTE Contrary to real situations, it is always assumed, for simplification, that the spectral distribution of the solar radiation (see Table 2) is not dependent upon atmospheric conditions (e.g. dust, mist, moisture content) and that the solar radiation strikes the glazing as a collimated beam and at normal incidence. The resulting errors are very small. 5.4.4 Solar direct reflectance The solar direct reflectance

of the glazing is calculated using the following formula:
(11) where
is the relative spectral distribution of the solar radiation (see Table 2);
is the spectral reflectance of the glazing;

is the wavelength interval. In the case of multiple glazing, the spectral reflectance

is calculated in accordance with 5.3. 5.4.5 Solar direct absorptance The solar direct absorptance

is calculated from Equation (8) in 5.4.2. 5.4.6 Secondary heat transfer factor towards the inside 5.4.6.1 Boundary conditions For the calculation of the secondary heat transfer factor towards the inside, , the heat transfer coefficients of the glazing towards the outside, , and towards the inside,

are needed. These values mainly depend on the position of the glazing, wind velocity, inside and outside temperatures and furthermore on the temperature of the two external glazing surfaces. As the purpose of this Standard is to provide basic information on the performance of glazing, conventional conditions have been stated for simplicity: kSIST FprEN 410:2010

FprEN 410:2010 (E) 14 a) position of the glazing: vertical; b) outside surface: wind velocity: approximately 4 m/s, corrected emissivity = 0,837; c) inside surface: natural convection, emissivity optional; d) air spaces are unventilated. Under these conventional, average conditions, standard values for

and
are obtained:
where

is the corrected emissivity of the inside surface. For uncoated soda lime silicate glass and borosilicate glass

and .

The corrected emissivity shall be defined and measured in accordance with EN 12898. NOTE Values lower than 0,837 for

(due to surface coatings with higher reflectance in the far infra-red) are only to be taken into account if condensation on the coated surface can be excluded. 5.4.6.2 Single glazing The secondary internal heat transfer factor, , of single glazing is calculated using the following formula:

(12) where
is the solar direct absorptance in accordance with 5.4.5;
and

are the heat transfer coefficients towards the outside and inside respectively in accordance with 5.4.6.1. 5.4.6.3 Double glazing The secondary internal heat transfer factor, qi, of double glazing is calculated using the following formula:

(13) where
and

are the heat transfer coefficients towards the outside and inside respectively in accordance with 5.4.6.1; kSIST FprEN 410:2010

FprEN 410:2010 (E) 15
is the solar direct absorptance of the outer pane within the double glazing;
is the solar direct absorptance of the second pane within the double glazing;

is the thermal conductance between the outer surface and the innermost surface of the double glazing (see Figure 4).

and
are calculated as follows:
(14)
(15) where

is the spectral direct absorptance of the outer pane, measured in the direction of the incident radiation, given by the formula:

(16)

is the spectral direct absorptance of the outer pane, measured in the opposite direction to the incident radiation, given by the formula:

(17)

is the spectral direct absorptance of the second pane, measured in the direction of the incident radiation, given by the formula:

(18)
and
are as defined in 5.4.3; ,
and
are as defined in 5.2. The thermal conductance

is determined by the calculation method in accordance with EN 673 whenever possible or by measuring methods in accordance with EN 674 or EN 675.

kSIST FprEN 410:2010
FprEN 410:2010 (E) 16
Figure 4 — Illustration of the meaning of thermal conductance

5.4.6.4 Triple glazing The secondary internal heat transfer factor of triple glazing, , is calculated using the following formula:

(19) where
is the solar direct absorptance of the outer pane within the triple glazing;
is the solar direct absorptance of the second pane within the triple glazing;
is the solar direct absorptance of the third pane within the triple glazing;
and

are the heat transfer coefficients towards the outside and inside respectively in accordance with 5.4.6.1;

is the thermal conductance between the outer surface of the first pane and the centre of the second pane (see Figure 5);

is the thermal conductance between the centre of the second pane and the innermost surface of the third pane (see Figure 5).

kSIST FprEN 410:2010
FprEN 410:2010 (E) 17
Figure 5 — Illustration of the meaning of the thermal conductances
and
and
are calculated as follows:
(20)
(21)
(22) where ,
and
are as defined in 5.4.6.3;

is the spectral direct absorptance of the second pane, measured in the opposite direction to the incident radiation, given by the formula:

(23)

is the spectral direct absorptance of the third pane, measured in the direction of the incident radiation, given by the formula: kSIST FprEN 410:2010

FprEN 410:2010 (E) 18
(24)
and
are as defined in 5.4.3. The thermal conductances
and

are determined in accordance with 5.4.6.3. 5.5 UV-transmittance In the UV range, the global radiation of the sun contains components in the UV-B range 280 nm to 315 nm and the UV-A range 315 nm to 380 nm. A standard relative spectral distribution for the UV part of the global solar radiation, , is given (see D.4). Table 3 gives the values of

for wavelength intervals of 5 nm in the UV range. The table has been drawn up with relative values in such a way that

for the total UV range. The UV-transmittance
is calculated as follows:
(25) where
is the spectral direct transmittance of the glazing (see 5.2);
is the relative distribution of the UV part of global solar radiation;

is the wavelength interval. NOTE If statements are made about the UV transmission of glazing, in most cases it is sufficient to give , the transmittance for the total UV radiation contained in global solar radiation. Only in special cases would there be any interest in the transmittances for the sub-ranges UV-A and UV-B. 5.6 Colour rendering The colour rendering properties of glazing in transmission are expressed by the general colour rendering index . This index enables to express synthetically a quantitative evaluation of the differences in colour between eight test colours lighted directly by the reference illuminant D65 and by the same illuminant transmitted through the glazing (see D.5). NOTE D.5 suggests to determine the colour rendering index with the help of a diskette. The user should be aware of the fact that the program contained in the diskette automatically compares the light filtered by a given glazing with the illuminant having the nearest colour temperature, rather than with D65. The test colours are defined by their spectral reflectance

(i from 1 to 8), reported in Table 4 (see D.5). The relative spectral energy distribution of illuminant D65 is reported in Table 5 (see D.2). The procedure to determine the general colour rendering index is the following. Calculate the tristimulus values , ,

of the light transmitted by the glazing:
(26) kSIST FprEN 410:2010
FprEN 410:2010 (E) 19
(27)
(28) where

is the relative spectral energy distribution of illuminant D65 reported in Table 5 (see D.2);

is the spectral transmittance of the glazing; , ,

are the spectral tristimulus values for the CIE 1931 colorimetric standard observer reported in Table 6 (see D.2). Calculate the tristimulus values of the light transmitted by the glazing and reflected by each of the eight test colours:

(29)
(30)
(31) where

is the spectral reflectance of each test colour i (i from 1 to 8). Calculate the trichromatic coordinates in the CIE 1960 uniform chromaticity diagram. The following formulae shall be used:  for transmitted light:

(32)
(33)  for light transmitted then reflected by the test colour i:
kSIST FprEN 410:2010
FprEN 410:2010 (E) 20
(34)

(35) Calculate the trichromatic coordinates corrected in terms of distortion by chromatic adaptation, fo

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